Battery
 

Couple of ?'s- 1. How many times should/can I charge my battery before I replace it? 2. Which widely avail. battery should I use, avail. AutoZone, Napa, Ect.. I am 100 miles from my nearest BMW dealer and don't want to drive down there for a battery.

I've "trickled charged" my oe batt, hundreds of times: it lasted 6 yrs.
I've trickled charged my replacement batt, dozens of times; it's still
going strong. Same for my Vette and, m'cycles.

If you are using a battery maintenance, low amp, floating type of
charger, it should last several years; if you are using a higher amp
or hot shot type of charger, forget it.

The AZ heat is tougher on batts, than MN cold, imo.

You don't give any details on car type, age, how old is your batt, etc.,
so specific recommendations are difficult.
AutoZone sells a Duralast which gets good reviews. Batteries Plus
has several for X5s, as do other car parts joints. You do not need
a "BMW" branded battery.

Whatever batt you get, bring it home and trickle charge it for a day+ to
get it slowly up to snuff, imo. New batts off the shelf, are seldom fully
charged and, resist the temptation/offer to have the selling store "charge
it" for you...
GL, mD

It's a 06' 3.0L, 48k miles, the problem is I don't drive it enough. Only about 2k miles in the last year. It could go weeks w/o even being started, but the last two times it has sat for 4-5 days, it's been low enough to not start, but all lights, radio, ect. work. Charge it for a couple hours and it's fine.

Get your new batt, and buy one of these:
Battery Tender Plus - Batterytender.com

On the web, for < $50. Be sure to get the alligator clips: they clip on,
under the hood. Keep it hooked while sitting, or every few days for a
24 hr period.

Besides the AZ heat, the Tender will keep your new batt working for years.
Or, buy the Tender and put it on your current batt:
it will bring it back as far as it can, but the current batt may be near termination.
GL, mD

Ditto on everything motordavid said. since you drive it so infrequently, you definitely need a trickle charger. BMW also offers (was $80) a charger that plugs into the lighter.

Personally, 5 yrs and it's gone. need it or not. I did see the Interstate battery truck deliver to my dealer. Go with after market & save $150 vs dealer costs

Battery in my 04 e53 lasted me 5 years before it went dead on me. Replaced it with an Autozone one after hearing good reviews on it. Been fine ever since.

Walmart has an EverStart thats pretty inexpensive and decent for around 75 bucks. Pep Boys has the Bosch brand one for about 139.99. IMO you dont need a BMW branded one. Their batteries are now being distributed by Exide Batteries, so its not like there's anything special about it.

There's a lot of variables that determine battery life so the only reliable gauge is how long your previous battery lasted. This is assuming you haven't changed your driving habits or place of residence.

I just changed my battery last week on my 330xi. It lasted 10 years. I don't do many short trips or sit parked with the stereo on. Cranked up perfectly fine last winter down to -30 C. As Md said, trickle charge your new battery when you get it. My new Exide 94R was on a smart charger for about 8 hours before it registered "full".

Installed the Walmart option for 73 bucks last February and it works/performs flawlessly.

Most likely the battery not able to hold a charge, I have let my OEM 6 year old battery sit for 5 mouths. Came back and it started on the first try.

Just bought an Everstart Maxx from Walmart, $77. Autozone and Batteries Plus wanted right at $150.